Apparatus for the decomposition of alkali amalgams



M 1, 1951 c. DEPREZ ETAL APPARATUS FOR THE DECOMPOSITION 0F ALKALI AMALGAMS F iled March 5, 1947 2 Sheets-Sheet 1 1/1 &////////M V/ sa Y nrw 5 wk; N m w N r m5 A May 1, 1951 c. DEPREZ ET AL 2,551,248

APPARATUS FOR THE DECOMPOSITION 0F ALKALI AMALGAMS Filed March 5, 1947 2 Sheets-Sheet 2 IN VENTORS Char/t; 08 A/em'; 545 Wf/f' Patented May 1, 1951 APPARATUS FOR THE DECOMPOSITION OF ALKALI AMALGAMS Charles Deprez, Uccle-Brussels, and Alexis Basilewsky, Bortsfort-Brussels, Belgium, assignors to Solvay & Cie, Ixelles-Brussels, Belgium, a

Belgian company Application March 5, 1947, Serial No. 732,571 In Belgium February 9, 1944 Section 1, Public Law 690, August 8, 1946 Patent expires February 9, 1964 4 Claims.

The invention concerns the manufacture of caustic alkali lyes starting from alkali amalgams obtained by electrolysis in a cell with a mercury cathode.

Decomposition of the alkali amalgam is usually elfected in an elongated vessel termed a pile, in the presence of catalysts in contact with the said amalgam and with the aqueous solution of alkali hydroxide. It is known that the decomposition reaction is more rapid when the resistance of the pile is weaker; for this reason the catalysts are immersed in the amalgam in such a manner as to secure as great a surface contact as possible. It is also known to cause a stirring up of the amalgam in order to renew constantlythis surface in such a manner as to assist decomposition, this, result being secured by the circulation of the amalgam whose layer is separated to flow in streamlets along the catalyst. As practised hitherto, the process is really only efiective in presence of thick layers necessitating the immobilization of relatively large quantities of'mercury.

The process and apparatus of the invention have for their object to avoid this disadvantage whilst ensuring a better electrical contact between the amalgam and the decomposition catalyst. They make use of the property that flat amalgamable surfaces present of being easily wetted by the mercury, which spreads and runs in a very thin layer.

According to the new process there is maintained methodically the flow of the amalgam in a thin layer on a conducting and amalgamable surface and there is secured by the intermediary of this surface, an extended contact between the amalgam and the catalyst, so as to make up for the small extent of the direct contact between them. In the arrangement utilized for putting the process into operation, the surface on which the amalgam flows is constituted by a metal plate against which is applied, over all its surface, a catalytic body in the form of a grid, the Whole being arranged in an enclosure containing the solution of alkali hydroxide. To ensure good contact between the catalyst and the plate, the lower surface of the grid is preferably mounted and clamped by mechanical means against the plate. According to the capacity of the installation several elements formed of plates and grids may be grouped in series, in parallel or in series parallel.

In another embodiment of our invention we use the bottom surface of the cell as the amalgamable surface in which mercury is caused to flow in contact with the catalyst, The latter is preferably made of separate parts, for example in the shape of bars, which are fitted in crosspieces and pressed against the bottom of the cell by a screw bearing on its cover or top.

The drawing represents diagrammatically some examples of carrying out this arrangement:

Fig. 1 shows in transverse section and Fig. 2 in side elevation a decomposition element formed of a plate and a grid.

Figs. 3, 4, 5 and 6 show different methods of grouping similar elements in a common container.

Fig. 7 is a longitudinal section of a part of a cell with an amalgamable bottom and Fig. 8 is a cross-sectional View of the same.

The arrangement represented in Figs. 1 and 2 comprises a rectangular flatplate a, whose three edges b are slightly raised, the fourth 0 being bent downwardly in such a manner as to form a shallow flow trough. This plate can be of pure iron, copper, steel, or any other conducting and amalgamable material. 0n the plate a is fixed the grid of non-amalgamable material d, such as graphite, the vertical portions of the grid d which rest upon the plate a being joined by transverse ribs d.

One face of the grid is carefully prepared so as to present a good flat surface assuringthe gridplate contact. Fixing, rigid for preference, is effected by bolts e, or by screws, straps or by other suitable mechanical means.

The amalgam poured on the plate spreads over it in a very thin layer; the quantity of mercury present on a grid is very small and the decomposition of the amalgam, per unit of volume, is very rapid. I

This arrangement is also advantageous in this sense, that the amalgam is no longer required to circulate at the bottom of the decomposition cell or apparatus; in consequence this latter may be constructed in any materials whatsoever provided they are resistant to the action of the alkali lyes. The invention, however is also applicable to apparatus of conventional shape in which the amalgam circulates at the bottom thereof, the amalgamable surface then being provided on said bottom surface.

It will be understood, therefore, that the said apparatus can take various forms, some of which being less cumbersome than the horizontal vessel of current use. Thus, elements such as illustrated in Figs. 1 and 2 can easily be mounted in such a manner that with respect to the circulation of the amalgam they are arranged in series, in parallel or in series parallel.

Thus, for example, they will be placed substantially horizontal one following the other, so that the edge of any one empties inside the edge b of the following one (Fig. 3). One can also place them one. above the other (Fig. 4) or arrange them vertically (Fig. 5). These various dispositions can be intercombined and form a:

battery (Fig. 6 for example), which is particularly advantageous, when several electrolytic cells discharge their amalgam in the same decomposition apparatus or when one desires to reduce the bulkiness of the latter. In the case of Fig. 6, the walls of the container follow the general form of the battery.

The catalysts represented are presented in the form of an integral grid; these grids may beconstructed as an assembly of separate elements as will now be described with reference to'Figs. '1 and 8.

In direct contact with the bottom 9 of atrough made of iron, steel, or other amalgamable metal, are bars h of graphite or other conducting, nonamalgamable material. These bars of upwardly flaring cross-section are placed at a small distance from each other and provided on their top faces with notches i adapted to fit in corresponding notches provided in' cross-pieces It. On these cross-pieces bears a metal armature k on which presses a vertical screw l adjustable in a nut m secured to the top wall or cover n of the apparatus.

This apparatus is very simple and convenient and permits of readily providing, and if necessary restoring, the requisite intimate contact between the bottom surface g and the grid elements h.

We claim:

In an apparatus for the decomposition of alkali amalgams, the combination with a receptacle for containing an aqueous solution of alkali hydroxide, of a plurality of inclined plates of amalgamable metal arranged in superposed spaced relationship in said receptacle, catalytic non-amalgamable grids having a smooth surface in intimate contact with a portion of the surface of each of said plates, said plates being arranged in a plurality of parallel series, with the lower edge of each plate overlying the higher edge of the next subjacent plate, the inclined plates in each of said series being spatially disposed in such manner that amalgam will flow in a thin layer successively over the upper surfaces of said plates in downward progression.

2. In an apparatus for the decomposition of alkali amalgams, the combination with a receptacle for containing an aqueous solution of alkali hydroxide, of a plurality of plates disposed in said receptacle in spaced relationship to the bottom of said receptacle, each of said plates having an amalgamable surface, catalytic nonamalgamable bodies in intimate contact with a portion of the amalgamable surface of each of said plates, whereby amalgam flowing in a thin layer over the amalgamable surfaces. of said plates is simultaneously in contact with a catalytic non-amalgamable body, said plates being spatially disposed in said receptacle in such manner that the amalgamable surface of each plate is in downwardly-inclined, vertically-spaced noncoplanar relationship with the amalgamable surfaces of. the other plates, with the lower edge of each plate overlying the higher edge of the next subjacent plate, whereby amalgam will flow in a thinlayer successively over the amalgamable surfacesof each of said plates in downward progression.

3. Apparatus as defined in claim 2 wherein each of said plates is rectangular in shape and has. three edges slightly raised and a fourth bent downwardly thereby to form a shallow flow channel for the amalgam.

4. In an apparatus for the decomposition of alkali amalgams, the combination with a receptacle for containing an aqueous solution of alkali hydroxide, of a plurality of downwardlyinclined plates disposed in said receptacle in spaced relationship to the bottom of said receptacle, each of said plates having an amalgamable metal surface adapted to receive a thin layer of flowing amalgam thereon, and a catalytic nonamalgamable body firmly clamped to a portion of the amalgamable surface of each of said plates, whereby amalgam flowing in a thin layer over the amalgamable surfaces of said plates is simultaneously in contact with a catalytic nonamalgamable body, said plates being arranged in said receptacle in vertically-spaced, noncoplanar downwardly progressing series relationship, the lower edge of each plate being spaced from and overlying the higher edge of the next subjacent plate.

CHARLES DEPREZ. ALEXIS BASILEWSKY.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 627,193 Kelly June 20, 1899 733,643 Gurwitsch July 14, 1903 908,545 Carrier Jan. 5, 1909 2,226,784 Sorenson Dec. 31, 1940 2,232,128 Muller Feb. 18, 1941 2,316,685 Gardiner Apr. 13, 1943 2,334,354 Richardson Nov. 16, 1943 

1. IN AN APPARATUS FOR THE DECOMPOSITION OF ALKALI AMALGAMS, THE COMBINATION WITH A RECEPTACLE FOR CONTAINING AN AQUEOUS SOLUTION OF ALKALI HYDROXIDE, OF A PLURALITY OF INCLINED PLATES OF AMALGAMABLE METAL ARRANGED IN SUPERPOSED SPACED RELATIONSHIP IN SAID RECEPTACLE, CATALYTIC NON-AMALGAMABLE GRIDS HAVING A SMOOTH SURFACE IN INTIMATE CONTACT WITH A PORTION OF THE SURFACE OF EACH OF SAID PLATES, SAID PLATES BEING ARRANGED IN A PLURALITY OF PARALLEL SERIES, WITH THE LOWER EDGE OF EACH PLATE OVERLYING THE HIGHER EDGE OF THE NEXT SUBJACENT PLATE, THE INCLINED PLATES IN EACH OF SAID SERIES BEING SPATIALLY DISPOSED IN SUCH MANNER THAT AMALGAM WILL FLOW IN A THIN LAYER SUCCESSIVELY OVER THE UPPER SURFACES OF SAID PLATES IN DOWNWARD PROGRESSION. 